The present invention relates to devices for acquiring and storing digital data representing waveforms and in particular to a method and apparatus for compactly displaying such acquired and stored data.
Many devices, such as logic analyzers, sample waveforms at regular intervals and generate digital data representing the state or the magnitude of the waveform at the moment of sampling. The data is typically stored in a random access memory (RAM) to be used subsequently in generating representations of the sampled waveforms on a cathode ray tube screen. In the past few years, the cost of random access memory has decreased such that it has become economical to use relatively large acquisition memories in logic analyzers, permitting the storage of large amounts of data representing long or frequently sampled waveforms.
Logic analyzers have typically reproduced the sampled waveforms on a screen in graphical form. As the detail and the length of the waveforms stored in memory have increased, simple reproduction of an entire stored waveform is not possible, even with the use of large, high resolution screens. Use of state displays has allowed acquired waveform information to be more compactly displayed. In a state display, the state of a waveform or a set of waveforms is represented by a number displayed at each sampling interval. While this allows waveform data to be compactly displayed, it is not in a form which is easily assimilated by most logic analyzer users, since most users think of waveforms in a graphical, rather than a numeric form, and the numeric state display is not well adapted for depicting the temporal relationships between two waveforms in an easily recognizable manner.